- Boost-users - lists.boost.org

typesafe typedef that is not implicitly convertible
by pwm 23 Jan '07

23 Jan '07

I am unable to find it now, but I thought I saw that there is a boost way to define a typedef using a unique class that cannot be implicitly converted to another type. Thus, typedef int Foo; void bar( Foo a ); would compile only with bar( Foo(3) ) not bar(3) Is this capability in Boost 1.33 or am I hallucinating? Thanks, Phil

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Re: [Boost-users] [general question] on threading anddoublecheckedlocking pattern
by Sohail Somani 23 Jan '07

23 Jan '07

Actually, its not so much wrong as it is "working currently but will probably break at some stage". Apparently, since Solaris always runs in "total storage ordering" mode, their implementation of pthread_once is correct for those hardware platforms. Just thought I'd clarify that. > -----Original Message----- > From: Sohail Somani > Sent: Monday, January 22, 2007 7:25 PM > To: 'boost-users(a)lists.boost.org' > Subject: RE: [Boost-users] [general question] on threading > anddoublecheckedlocking pattern > > Oopsie: > > http://bugs.opensolaris.org/view_bug.do?bug_id=6513516 > > So even the smart guys get it wrong. > > > -----Original Message----- > > From: boost-users-bounces(a)lists.boost.org > > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > > Sohail Somani > > Sent: Monday, January 22, 2007 5:12 PM > > To: boost-users(a)lists.boost.org > > Subject: Re: [Boost-users] [general question] on threading > > anddoublecheckedlocking pattern >

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Re: [Boost-users] [general question] on threading anddoublecheckedlocking pattern
by Sohail Somani 23 Jan '07

23 Jan '07

Oopsie: http://bugs.opensolaris.org/view_bug.do?bug_id=6513516 So even the smart guys get it wrong. > -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Sohail Somani > Sent: Monday, January 22, 2007 5:12 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [general question] on threading > anddoublecheckedlocking pattern

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[multiindex] key extractor as free function - how?
by Markus Werle 23 Jan '07

23 Jan '07

Hi! I read from the docs that we can define key extractors to be one of - identity - member - mem_fun - composite_key Is it possible to use a free function as key extractor in the same way as the ones listed above and can you give an example of this? reagrds, Markus

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Where to get boost 1.32 for solaris c++
by Victor Cheng 23 Jan '07

23 Jan '07

It seems that sun c++ has problems compiling boost 1.33.1 and the most compatible version is 1.32, but I could not find it any where on www.boost.org. It's probably in the cvs repository, but can't find the tag for 1.32. Is there a place where I can download this version?

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[multiindex] combination with boost::tuple
by Markus Werle 23 Jan '07

23 Jan '07

Hi! I'd like to use boost::tuple in a list-replacing multiindex and use the first entry in the tuple as key. The following fails to compile. Could you please provide a correction? #include <boost/tuple/tuple.hpp> #include <boost/multi_index_container.hpp> #include <boost/multi_index/sequenced_index.hpp> #include <boost/multi_index/key_extractors.hpp> namespace bm = ::boost::multi_index; class C { typedef boost::tuple<std::string, std::string> data_t; template <typename T> struct mutable_value { mutable_value(const T& t):t(t){} operator T&()const{return t;} private: mutable T t; }; typedef bm::multi_index_container <mutable_value<data_t>, bm::indexed_by <bm::sequenced<>, bm::ordered_unique <bm::mem_fun<data_t, std::string, &data_t::get<0> > > > > storage_t; storage_t storage_; }; int main() { C c; }

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compiling boost using codewarrior for windows
by Jean-Marc 23 Jan '07

23 Jan '07

when compiling boost ( the cvs version ) with metrowerks codewarrior for windows, I get a huge amount of errors. Is this (great !) compiler supported by boost ? Many thanks for your help Regards JM

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[pool] fixed-size allocation pool
by Michael Marcin 23 Jan '07

23 Jan '07

I was wondering if I could use boost::pool for a fixed-sized object pool and return NULL if it tries to construct more than the maximum. Reading http://www.boost.org/libs/pool/doc/implementation/object_pool.html it seems like I could if I set_next_size(0) but it explicitly says I should not do that. Is there a reason to not support this behavior or is it supported in some other way/library? Thanks, Michael Marcin

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Re: [Boost-users] [general question] on threading and doublecheckedlocking pattern
by Sohail Somani 23 Jan '07

23 Jan '07

It definitely is. But if you could find a way to make it better, even with complicated and platform-dependent code, and then wrap it up into something usable, have it tested and peer-reviewed, and placed somewhere we could all use it, it would still be useful. -------------- Sure -------------- P.S. In this particular case, I don't think you can get better than: - a read barrier and if-branch in the already-initted case - that + a write barrier in the init case - all wrapped into a single int. which is slightly, but not much better than a mutex. It is also slightly better than most implementations of boost::once/pthread_once, and much better than some, depending on platform. -------------- What I've found that pthread_once implementations end up using DBCL anyway but the benefit of using it there is obviously that you don't have to debug it since they put in the necessary barriers. As far as I'm concerned the problem is solved. For the 0.0001% of C++ programmers that actually need the performance and are willing to shell out the debugging hours, they are more than welcome. I (personally) think a boost singleton based on boost once would be good enough for everyone else until there are solutions per os/hw combination. Do you think people would like one? Not to take away from your valid points of course. Sohail

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Re: [Boost-users] [general question] on threading and double checkedlocking pattern
by Sohail Somani 22 Jan '07

22 Jan '07

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Ovanes Markarian > > I might be wrong here, but I would like to hear some thoughts > of C++ professionals. > > I read in lots of sources about DCLP and how it is broken in > conjunction with Singleton pattern > and my question is of a very simple nature. Is it possible to > solve this problem by introducing > function calls via function pointers? Or is there still a > way, that these calls might be inlined > and if yes then how could this look like? This example is not > about freeing the singleton, it is > just about creating it. Hi, Perhaps the path-of-least-debugging is to use boost::once? Sohail

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